Charan, I’ll agree with Larry and expand on a one of his comments. Enterprise Project Types (EPTs) have associated work flows and PDPs. When you create a new project in PRO and then save it up to PWA, that project has no associated EPT and it also has no associated PDPs. If your organization uses PDPs to exclusively update project level data (as our organization does), you will not be able to access any project level fields until someone manually attaches the workflow and PDPs to the schedule you just uploaded.
Note that there are some project level data fields types, such as multi-line text fields, that can only be updated via PDPs.
Beyond that, our organization uses EPTs as a means to ensure that each new schedule starts with the correct schedule template.